With development of communications services, location services are playing an important role as an indispensable part of mobile communication and personal communication services. The location service is a value-added service that obtains location information, namely, longitudinal and latitudinal coordinates, of a mobile terminal user by using an operator network (for example, an LTE network) and provides a corresponding service for the user with support of an electronic map platform. In recent years, with unceasing improvement of people's material standards of living, people are having increasingly high requirements on location services, for example, extensive requirements on positioning in aspects such as security surveillance, emergency rescue, and travel guide.
Currently, a positioning method based on a time difference of arrival (TDOA) is an important method for implementing the location service. Depending on different reference signal directions, the TDOA-based positioning method may be divided into positioning based on an observed time difference of arrival (OTDOA) and positioning based on an uplink time difference of arrival (UTDOA). A basic principle of the TDOA-based positioning method is as follows: When there are three or more base stations in a system, a location of user equipment (UE) may be determined based on reference signal time differences (RSTD) of positioning reference signals (PRS) that are sent simultaneously by different base stations and transmitted in a downlink direction or of sounding reference signals (SRS) that are sent simultaneously by the UE to different base stations and transmitted in an uplink direction.
However, because the different base stations have different local oscillators, or because of another reason, different absolute times are generated. As a result, signals generated from or signals received by antenna ports of the base stations are not absolutely time-synchronized. This is referred to as a time alignment error (TAE). When the TDOA-based positioning method is used for positioning, the TAE is added to the RSTD, leading to an error in TDOA-based positioning, so that TDOA-based positioning is undesirably accurate.